Method for clarifying industrial wastewater while minimizing sludge

ABSTRACT

Methods are described for removing contaminates from aqueous industrial wastewater process streams, specifically industrial laundries to yield a less contaminated aqueous effluent for discharge to a sewer and reduce the sludge generated therefrom. A premixed medium/high molecular weight and medium/high charged cationic coagulant solution polymer and an inorganic aluminum species is injected into the wastewater, and after at least a two second delay, a high molecular weight highly charged anionic flocculent polymer solution is injected into the wastewater which reduces sludge generation, while maintaining or exceeding effluent quality. Also, no coagulant, flocculent or sludge aids are needed to attain the results and the sludge can be dewatered in a plate and frame press.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 10/827,141filed Apr. 19, 2004, now U.S. Pat. No. 7,160,470.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not Applicable.

TECHNICAL FIELD

This invention is directed to methods of clarifying industrialwastewater, specifically industrial laundry wastewater that includeswastewater from light to heavy product mix industrial laundry plantsutilizing both full and split streams as defined by a client-user.

BACKGROUND OF THE INVENTION

In the laundry wastewater treatment field of solids/liquid separation,suspended and emulsified solids are removed from water by a variety ofprocesses, including sedimentation, straining, flotation, filtration,coagulation, flocculation, and emulsion breaking among others.Additionally, after solids are removed from the wastewater they mustoften be dewatered. Liquids treated for solids removal often have aslittle as several parts per million (ppm) of suspended solids ordispensed oils, or may contain several thousand ppm of suspended solidsor oils. Solids being generated as sludge may contain anywhere from 0.1to 6 weight percent solids prior to dewatering, and from 20 to 50 weightpercent solids material after dewatering by a plate and frame press.Solids/liquid separation processes are designed to remove solids fromliquids and the more solids generated in the process, the more costlyits disposal.

While strictly mechanical means have been used to effect solids/liquidseparation, the modern methods often rely on mechanical separationtechniques that are augmented by synthetic and natural polymericmaterials to accelerate the rate at which solids can be removed fromwater. These processes include the treatment of wastewater with cationicorganic and inorganic coagulants that coagulate suspended particulatesto form larger particles that then may be brought together by an anionicflocculent to create particles large enough to be removed from the wastestream by mechanical means, i.e., flotation or clarification, and makethe effluent suitable for industrial reuse or disposal in compliancewith local permit discharge requirements.

In the industrial laundry industry, the chemical treatment of wastewaterto a typical municipal standard of 100 ppm of oil and grease (EPA method1664) prior to the introduction of this invention has been: thehydraulic equalization of untreated wastewater followed by the meteredflow of the wastewater through a pipe or tanks to provide for retentiontime for the injection of a variety of chemicals including combinationsand individually, both organic and inorganic coagulants and aids,followed by an organic component flocculent to produce coagulation andflocculation. These inorganic components used for coagulation orcoagulation aids, typically have simple hydration factors ofapproximately 6-12 water molecules and may also be used in conjunctionwith a separate component, i.e. perlite or diatomaceous earth orbentonite clay, to act as a “body builder” to produce sludge so that indown stream processes it may be dewatered. A variety of organic andinorganic coagulants and aids exist throughout the marketplace.Historical data has shown that used in correct combination thesechemistries can produce suitable effluent with sludge generation ofapproximately 1.1 to 2.5% of influent flow, whereas by use of thisinvention sludge production is reduced to approximately 0.25 to 1.0% ofinfluent flow.

Chemical treatment generally refers to the removal of nonsettleablematerial by coagulation and flocculation. Chemical treatment forwastewater clarification is typically employed when colloidal andmicroemulsified solids need to be removed so that the total petroleumhydrocarbons (TPH), fat, oil and grease (FOG), biochemical oxygen demand(BOD), chemical oxygen demand (COD), total suspended solids (TSS), andother contaminants being discharged to a receiving stream need to beminimized. Typically, such treatment comprises using a cationiccoagulant with one or more inorganic components, injected in combinationor individually, followed by an anionic flocculent. Coagulation is theprocess of destabilization of the colloid waste particle by causing thecoagulant (at 50-1000 ppm) to absorb by means of charge neutralizationto form microfloc and impart residual cationic surface charge of thecoagulated particles. The second step is to introduce a coagulant aid,i.e., ferric chloride, aluminum sulfate, ferrous sulfate, calciumchloride, polyaluminum chloride, typically at a rate of 75-700 ppmdepending on the species, to increase the ability to form a more highlycationic surface that will cause the further adsorption of thecoagulated particles onto the surface of an additional chemical, usuallybentonite clay, at 200-900 ppm through a “sponge” effect. Flocculationoccurs when the highly charged anionic flocculent bridges the previouslyformed cationic particles. Once neutralized, particles no longer repeleach other and can come together to form larger agglomerated solids orsludge, which may then be removed from the water. The third step that isoccasionally taken is the addition of sludge thickeners that assist inallowing the sludge to dewater, i.e. perlite, bentonite clay,diatomaceous earth and others. This invention is specifically directedto eliminating the second and/or third steps, i.e., the addition ofcoagulant aids and/or sludge thickeners and a resultant reduction of theformation of sludge by up to 80% compared to previous historically usedmethods.

Clarification chemicals are typically utilized in conjunction withmechanical clarifiers including dissolved air flotation systems (DAFs),induced air flotation systems (IAFs), and settlers for the removal ofsolids from the treated water. The clarification chemicals coagulateand/or flocculate the suspended solids into larger particles, which canthen be removed from the water by gravitational settling, flotation, orother mechanical means.

Processes for the preparation of high molecular weight cationicdispersion polymer flocculents are described in U.S. Pat. Nos. 5,006,590and 4,929,655. High molecular weight, high active polymer cationicsolution polymers for water clarification, dewatering and retention anddrainage are disclosed in U.S. Pat. No. 6,171,505.

BRIEF SUMMARY OF THE INVENTION

The invention is directed to methods of clarifying industrialwastewater, specifically industrial laundry wastewater, to produce acompliant effluent and a reduction of sludge of between 30%-80%, using atwo part system of a pDADMAC/ACH blended coagulant followed by apoly(acrylamide-co-acrylate) flocculent. Furthermore, the sludgeproduced using this invention will dewater in a typical plate and framepress without the use of any other organic or inorganic compounds addedto the waste stream or sludge.

This invention pertains to the use of a cationic aqueous solutioncontaining a mostly equal blend of a 50% ratio of approximately a 2-35%concentration of solids by weight of polydiallyldimethylammoniumchloride (pDADMAC) organic polymer and a combination ofepichlorohydrin-quaternaryammonium species where pDADMAC is the majorconstituent, together with approximately 5-40% concentration of solidsby weight of aluminum chlorohydrate (also known by other names i.e. ACH,also known as partially neutralized polyaluminum chloride) an inorganiccompound utilized as a coagulant (along with a combination of otherchloride species where ACH is the major constituent) in the chemicaldemulisification of laundry wastewater to produce catatonic chargedparticles.

The wastewater is cleaned using a medium to high molecular weight mediumto very highly charged cationic solution coagulant (polymer) premixedwith an inorganic aluminum species as one product, followed by a high tovery high molecular weight anionic flocculent, I.e.,poly(acrylamide-co-acrylate), (also known herein as sodium acrylateflocculent) with a 35% charge or higher (preferably 50% or higher),added in solution to produce particulate of sufficient size to beremoved by physical means without the use of secondary, tertiary, orquaternary coagulation or flocculation aids. The wastewaters, to whichthis invention is directed, may be produced by the industrial cleaningof products including but not limited to: uniforms, shop towels, inktowels, mats, rugs, bar mops, aprons, coveralls and coats, used toprotect personnel from manufacturing or commercial wastes.

The creation of the wastewater stream can be through the use of allavailable commercial equipment that is used for washing the variousproducts. These streams must then be collected in such a way as topromote the batch collection or intermittent or continuous flow of thestream. This collection of wastewater then may be further treated bybatch or flow proportion as to allow for the injection and mixing oftreatment chemicals by primary coagulation and flocculation only. Thisinvention cleans the wastewater and reduces the sludge generation by asmuch as 80% from traditional methods of industrial laundry wastewatertreatment, resulting in the elimination of the need for additionalin-stream and downstream additives that may have been necessary incertain prior art methods as described above. Furthermore, at the properdoses, this invention allows the sludge to be dewatered in a typicalplate and frame press or other equipment used for the dewatering ofsludge.

The specific invention herein relates to the wastewater batch, or thein-stream use of the coagulant polymer compound containing pDADMACcoagulant and ACH injected into the wastewater stream in a diluted or anundiluted form, at any point prior to the sodium acrylate acrylamideflocculent injection with at least a two (2) second interval between theinjections. The coagulant must be injected in the correct empiricalquantity and given sufficient predetermined time to begin and completethe coagulation of the waste particles and the flocculent must beinjected in the correct empirical quantity and given sufficient time tobegin and complete the flocculation of the coagulated particles prior todewatering. The coagulant and flocculent must be injected in sufficientquantity to create the conditions in the sludge that allow for thedewatering of the sludge generated by this process. These injection ordosing ratios are critical to the overall performance in the preferredembodiment of the method of this invention.

The dry anionic flocculent is made into any solution strength commonlybetween 0.05-0.5%, 0.2% being preferred, and injected post coagulant byat least a two (2) second interval and in sufficient empiricalquantities as to cause coagulated wastewater to form flocculated wasteparticles of sufficient size to settle in clarification or rise byflotation, as by dissolved/induced air or other means.

The combination of the coagulant and the flocculent in the waste-streamproduces a sludge volume 30-80% less than with those previous laundrywastewater treatments which utilize additional treatment chemicals oraids. The process testing of this invention has shown these reductionsto be typical of the specific application of the invention disclosedherein.

The flocculents of this invention must be of sufficient charge density,molecular weight and added in sufficient quantities, as to aid in alldewatering mechanisms, typically being a plate and frame press oftenfound in typical plants.

BRIEF DESCRIPTION OF THE DRAWING

The novel features which are believed to be characteristic of thisinvention are set forth with particularity in the appended claims. Theinvention itself, however, both as to its organization and method ofoperation, together with further objects and advantages thereof, maybest be understood by reference to the following description taken inconnection with the accompanying drawing, which illustratesschematically an industrial laundry wastewater treatment systemembodying features of this invention.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention, methods are provided forremoving contaminants from an aqueous solution.

Methods are provided for removing: surfactants, phenolics, totalpetroleum hydrocarbons, fats oil and grease, TSS contributors, BODcontributors, COD contributors, and TOC contributors from an aqueoussolution. The surfactants, phenolics, total petroleum hydrocarbons,fats, oil and grease (FOG), TSS contributors, BOD contributors, CODcontributors, and TOC contributors from an aqueous solution are removedby adsorption onto a carrier precipitate which is formed in situ withinthe aqueous solution. In each of the embodiments of the invention thepreferred method involves rapidly forming the precipitate.

The method of the invention can be used to remove the followingcontaminants from the laundry wastewater stream: TSS contributors, BODcontributors, COD contributors, TOC contributors, and/or fats, oil andgrease (FOG). The invention will now be described first with respect toFOG, TSS contributors, BOD contributors, COD contributors, and TOCcontributors. Unless otherwise stated, all process and apparatusparameters disclosed for FOG removal are equally effective for theremoval of the other contaminants as well. Likewise, unless otherwisestated, all process and apparatus parameters disclosed for the removalof the other non-volatile contaminants are equally effective for heavymetal removal as well.

“Coprecipitation” as used with respect to the invention described hereinrefers to the chemical phenomenon where, within an aqueous solutioncontaining a cationic carrier precipitate precursor, an anionic carrierprecipitate precursor, and one or more coprecipitant precursors, thecationic and anionic carrier precipitate precursors are caused tochemically react and precipitate out of the aqueous solution as carrierprecipitate particles; and, as the carrier precipitate particles areformed, coprecipitant precursors are removed from the aqueous solutionby adsorption onto the surface of the carrier precipitate particleand/or by occlusion within the interior of the carrier precipitateparticle.

The coprecipitant reaction is very rapid. Typically, more than 85 weightpercent, and usually more than ninety-nine (99) weight percent, of theoil and grease are removed from the waste solution within about oneminute after the formation of the agglomerated particle.

Finally, the methods of the invention are superior to conventionalprecipitation methods in that these methods also produce lessprecipitate sludge. The lower sludge production stems, in part, from theremoval of separately or blended inorganic components including but notlimited to: ferric chloride, ferrous sulfate, polyaluminum chloride,bentonite clay, perlite, diatomaceous earth, aluminum chloride (exceptfor the blend of 20% pDADMAC and 20% aluminum chlorohydrate used inaccord with this invention).

The aqueous polymeric coagulant pDADMAC is made by several manufacturersand of pre-described weight percent of solids combined with thepre-described aqueous polyaluminum chloride. The first chemical of theinvention is mixed in controlled conditions with water to produce acationic blend polymer and then injected into the waste stream inempirical quantities of 50-700 parts per million (ppm), dependingprimarily on stream flow rate or strength to cause the coagulation ofnegatively charged waste particles.

The resulting coagulated particles then have sufficient mass andresidual cationic charge to react with the subsequent addition of thepre-described, wetted, water dispersed dry anionic flocculent to createan agglomerated particle of sufficient size for removal by mechanicalmeans. The flocculent is injected into the waste stream after apredetermined time to permit the cationic blend to substantiallycomplete the coagulation of the particles by at least two (2) secondsafter the injection of the coagulant blend in empirical quantities of5-50 ppm. This dose of flocculent is critical to not only theflocculation of the coagulated particles but to the later dewatering ofthe sludge. If either insufficient or excessive flocculent is injectedinto the wastewater stream, the sludge will not appropriately dewater.

The time interval for the coagulant to sufficiently absorb the wasteparticles prior to injection of the flocculent must be no less than two(2) seconds and no longer than ten (10) minutes. Sufficient passive oractive mechanical action must take place between the wastewater and thecoagulant as to allow the intimate comingling of the waste particleswith the coagulant prior to addition of the flocculent.

The dry anionic flocculent must be of a molecular weight as termed inthe industry as “very high” and of a charge density of no less thanthirty-five percent (35%) but usually around fifty percent (50%). Againdepending on wastewater stream strength the preferred range of 7-30 ppmof flocculent is needed to flocculate the coagulated particles to alevel where the additional use of other coagulant aids and/or dewateringaids is not necessary.

Using this invention, typical sludge generation is reduced 30-80% whichequates to 0.2 to 0.6% of sludge being produced of the influent flow andafter typical dewatering using a plate and frame press the sludge isreduced another 50%. This compares to other typical treatments utilizingthe above described three part systems or others generating 0.8 to 2.5%of the influent flow as sludge. Dewatering characteristics of the sludgein other prior art systems vary from system to system and do cause anadditional “body feed” to the sludge in order to achieve dewaterability.

The following examples, are set forth to illustrate this invention andrender same more understandable but are not intended to limit the scopeof the herein disclosed and claimed invention.

EXAMPLE ONE

Laundry plant #1 with a daily average water usage of 110,000 gallons perday with 50% of the input product being shop towels, mats, ink wipersand other heavy soils was producing 1.1% of their daily wastewater asliquid sludge. The prior existing program being used for industrialpretreatment was a poly(diallyldimethylammonium chloride) solution witha dose rate of 200-500 ppm coupled with the use of a six percentbentonite clay fed at the rate of 600 ppm, residence time for eachchemical was 15-20 seconds at 125 gpm flow. This created coagulatedparticles that were then flocculated with a 0.2% polyacrylate flocculentat 6-8 ppm to produce particles able to be floated through mechanicalmeans. The plate and frame press produced dewatered sludge cakesamounting to 135 cubic feet per day.

The method of this invention was used to replace the then existingprogram with a dose rate of 200-400 ppm of coagulant using a mix time ofapproximately 20 seconds, and the application of the flocculent at 20-30ppm using a mix time of approximately 40 seconds, resulting in floc thatwas floated through mechanical means. The amount of sludge produced was0.3% of the influent flow thereby resulting in a dewatered sludgereduction of 66%. Since the application of this invention to plant #1,all required effluent parameters have been compliant with EPArequirements.

The effect on the plate and frame dewatering press was a reduction inthe final amount of dewatered sludge to 45 cubic feet per day, thusreducing disposal costs of the sludge, as well as substantial savings intreatment chemicals and other additives used in the prior program.

EXAMPLE TWO

A newly installed dissolved air flotation wastewater system at Plant #2began utilization of the methods of this invention for chemicaltreatment of the wastewater at start-up. The volume of water produced bythe facility was approximately 70,000 gallons per day and the productmix comprised mostly of heavily grease-laden linen from the foodindustry. The methods of the invention were applied at 300-600 ppm usinga mix time of approximately 15 seconds of coagulant and 2545 ppm offlocculent using a mix time of approximately 30 seconds, resulting infloc able to be floated through mechanical means, with a resultingsludge production of 0.3% of the influent flow. Since the application ofthe invention, all required effluent parameters have been compliant withEPA requirements.

Treatment in accord with this invention resulted in an influentreduction of 421 ppm of biochemical oxygen demand (BOD) to <5.3 ppm(method EPA 405.1), and 360 ppm to <5.0 ppm oil and grease (method EPA1664).

The effect on the plate and frame dewatering press was to produce only25 cubic feet of dewatered sludge per day.

These examples one and two exemplify the consistent results achievableby this invention. While the dewatered sludge from Plant #2 could havebeen expected to amount to about 28.6 cubic feet, if the wastewater fromthe two plants were the same. Also, the newer equipment and other noteddifferences in the dosage and differing effluents will cause variousresults while being considered consistent in accord with this invention.

EXAMPLE THREE

An industrial laundry with an average flow of 80,000 gallons per daytreated the wastewater with a pDADMAC coagulant coupled with an aluminumsalt (200400 ppm) injected prior to the transfer pump and bentonite clay(600-900 ppm) injected 15 seconds later and sodium acrylate flocculent(7 ppm) 15 seconds down stream. Water was non compliant with a readingof eight (8) on a standard turbidity wedge. Sludge production for thefacility was 1100 gallons per day. Filter cakes were not forming insideof the press which necessitated hauling away the liquid sludge.

After replacement of the above-described program with a new process inaccord with this invention using 250 ppm of coagulant injected prior tothe transfer pump and 30 ppm of flocculent injected at the former clayinjection point, sludge was reduced to 350 gallons per day. The plantbecame compliant with 35+ on a standard turbidity wedge. This newprocess formed sludge cakes by the press amounting to 7 cubic feet perday, and substantial savings in disposal costs were achieved.

Presented in Table 1 are the results of Total Contained Leaching Process(TCLP) data used for determining the long-term hazardous effects ofdewatered sludge in the industrial laundry of this Example Three. TheTCLP approximates under laboratory conditions what the sludge willdischarge during decomposition into the surrounding environment as knownhazardous components. Table 1 is the qualitative analysis of thosehazardous components taken from sludge cake utilizing a prior methodincluding bentonite clay (year 2002) and those utilizing the method inaccord with this invention (year 2003).

TABLE 1 TCLP 2002 TCLP 2003 Before Invention After Invention ANALYTERESULT UNITS RESULT UNITS METHOD BENZENE <0.001 ppm <0.01 ppm 8260CARBON TETRACHLORIDE <0.001 ppm <0.01 ppm 8260 CHLOROBENZENE <0.001 ppm<0.01 ppm 8260 CHLOROFORM <0.005 ppm <0.01 ppm 8260 DICHLOROBENZENE,1,4- <0.005 ppm <0.016 ppm 8260 DICHLOROETHANE, 1,2- <0.005 ppm <0.01ppm 8260 DICHLOROEHTYLENE, 1,1- <0.005 ppm <0.01 ppm 8260 METHYL ETHYLKETONE <0.019 Ppm <0.01 ppm 8260 TETRACHLOROETHYLENE <0.017 Ppm <0.113ppm 8260 TRICHLOROETHYLENE <0.005 Ppm <0.01 ppm 8260 VINYL CHLORIDE<0.002 Ppm <0.001 ppm 8260 CRESOL, M&P <0.1 Ppm <0.05 ppm 8270 CRESOL,0- <0.15 Ppm <0.1 ppm 8270 DINITROTOLUENE, 2,4- <0.01 Ppm <0.05 ppm 8270HEXACHLOROBENZENE <0.01 Ppm <0.05 ppm 8270 HEXACHLOROBUTADIENE <0.005Ppm <0.05 ppm 8270 HEXACHLOROETHANE <0.005 Ppm <0.05 ppm 8270NITROBENZENE <0.05 Ppm <0.05 ppm 8270 PENTACHLOROPHENOL <0.05 Ppm <0.05ppm 8270 PYRIDINE <0.1 Ppm <0.1 ppm 8270 TRICHLOROPHENOL, 2,3,5- <0.05Ppm <0.05 ppm 8270 TRICHLOROPHENOL, 2,4,6- <0.05 Ppm <0.05 ppm 8270CHLORDANE <0.01 Ppm <0.01 ppm 8270i ENDRIN <0.01 Ppm <0.01 ppm 8270iHEPTACHLOR <0.01 Ppm <0.008 ppm 8270i HEPTACHLOR EPOXIDE (BETA) <0.008Ppm <0.008 ppm 8270i LINDANE <0.01 Ppm <0.01 ppm 8270i METHOXYCHLOR<0.05 Ppm <0.01 ppm 8270i TOXAPHENE <0.1 Ppm <0.01 ppm 8270i 2,4 D<0.002 Ppm <0.02 ppm 8151 2,3,5-TP SILVEX <0.002 Ppm <0.02 ppm 8151ARSENIC, As <0.01 Ppm <0.001 ppm 7060 BARIUM, Ba 0.478 Ppm <0.1 ppm 7080CADMIUM, Cd <0.01 Ppm <0.01 ppm 7130 LEAD, Pb 0.051 Ppm <0.1 ppm 7421CHROMIUM, Cr 0.049 Ppm <0.01 ppm 7190 MERCURY, Hg <0.001 Ppm <0.02 ppm7470 SELENIUM, Se <0.02 Ppm <0.02 ppm 7740 SILVER, Ag <0.005 Ppm <0.05ppm 7760 METALS, DIGESTION FOR 1 ea sample 1 ea sample 3030 D SOLIDS 100Percent 100 percent 1311 CORROSIVITY Ph >12.5 or <2 5.1 Units 5.9 units9040 IGNITABILITY >140 F. >140 F. 1010 TOTAL RELEASABLE CYANIDE <0.01mg/kg <0.009 ppm 9010 TOTAL RELEASABLE SULFIDE <0.5 mg/kg <0.5 ppm 9030REACTIVITY = 0 Negative = 0 Negative Exam TCLP SEMI/NON-VOLATILES 1 ea 1ea 1311 EXTRACT TCLP VOLATILES EXTRACT 1 Ea 1 ea 1311It can be extrapolated from the above two sets of data that neither TCLPhas components in sufficient quantities as to categorize the sludge ashazardous under most current regulations for the disposal of sludge.

EXAMPLE FOUR

An industrial laundry whose wash mix is a majority of heavy soilproducts treated their wastewater with separately fed injections of 20%solids by weight pDADMAC (200-500 ppm) followed approximately 20 secondslater by a second injection of polyaluminum chloride (400-800) and inapproximately 10 seconds an injection of sodium acrylate flocculent toproduce EPA and municipal non-compliant effluent (eight on a standardturbidity wedge) and approximately 2200 gallons of sludge with a dailyflow of 120,000 gallons of wastewater per day. In order for the facilityto dewater the sludge by plate and frame press method, 350 pounds ofdiatomaceous earth was added as a body feed to produce a sludge cake.

After elimination of the previous treatment program and introduction ofthe methods in accord with this invention, the plant became compliant(35+ on a standard turbidity wedge) and the amount of sludge producedwas approximately 600 gallons per day. The body feed of Kenite(perlite), needed to produce sludge cake, was eliminated. The coagulantinjected at the intake side of the transfer pump was at 150-300 ppm andthe flocculent was injected approximately 20 seconds later at 35 ppm.Effluent testing done by a local laboratory showed total petroleumhydrocarbons to be 4 mg/l, which was well within EPA and municipallimits.

EXAMPLE FIVE

This plant was an industrial laundry with an average daily flow of70,000 gallons and a mixed product load requiring treatment of thewastewater to meet local limits. An epi-quanternary amine coagulant wasbeing injected prior to the wastewater transfer pump at 500 ppm with aninjection of technical grade ferric chloride at 250 ppm into a chemicalreaction tank with two minutes detention time at 75 gallons per minute.Then it was gravity fed to a second tank and a sodium acrylate emulsionpolymer was fed at 10 ppm. The sludge produced daily was approximatelyone percent (1%) of the daily flow (700 gallons) and was being hauledfor disposal as a liquid.

After removal of the above process and incorporating the process inaccord with this invention with the coagulant injection point being atthe first tank at 400 ppm and the flocculent fed at 25 ppm into thesecond tank, the effluent quality was clear at 35 on a standardturbidity wedge. Sludge was reduced to 0.5% (350 gallons) of theinfluent and was hauled for disposal as a liquid because this plant hadno plate and frame press.

EXAMPLE SIX

This plant was an industrial laundry out of compliance on allparameters. At 70,000 gallons per day the facility was producing 1100gallons of sludge and needed to add as much as 600 pounds of bentoniteclay for treatment and as a body feed for sludge dewatering. Thetreatment scheme utilized at the time was an epi-amine/DADMAC (400-600ppm) combination coagulant followed by bentonite clay injection(600-1200 ppm) and sodium acrylate flocculent (7-10 ppm).

As shown on Table Two, once the prior process was abandoned and theprocess in accord with this invention was introduced, the plant becamecompliant with local standards. Injection of the coagulant was madeprior to the intake side of the wastewater transfer pump with a fivesecond interval for the injection of the flocculent. Sludge was reducedto 300-350 gallons per day with 25 cubic feet of sludge being producedafter plate and frame dewatering.

TABLE TWO Before After PARAMETER LIMIT Invention Invention BIOCHEMICALOXYGEN 300 mg/L 1110 mg/L 120 mg/L DEMAND OIL & GREASE (TOTAL) 100 mg/L 187 mg/L  5.2 mg/L pH Acidic  <5.5 7.58 9.33 pH Basic >11.5 7.58 9.33TOTAL SUSPENDED SOLIDS 300 mg/L 1555 mg/L  26 mg/L

It is to be noted that under extremely limited conditions, a plant usingthe method of this invention may find it appropriate to introduce asmall amount of bentonite clay, for example, into the waste stream atapproximately two to six seconds after the addition of the coagulant andbefore the addition of the flocculent, in the herein disclosed method,as a sludge conditioner. Though this is not necessary with thisinvention, when the waste stream is extremely heavy in oil and greasecomponents (over 1000 ppm), the clay will assist in the dewatering ofthe sludge. The addition of the clay to be added should be in a muchsmaller quantity (less than 200 ppm) than used in the prior art methods,i.e., without the use of the present invention. The clay is used forconditioning the sludge only, and not for achieving effluent qualitystandards, which are attained without clay addition.

While the invention has been described with respect to certain specificembodiments, it will be appreciated that many modifications and changesmay be made by those skilled in the art without departing from thespirit of the invention. It is intended, therefore, by the appendedclaims to cover all such modifications and changes as fall within thetrue spirit and scope of the invention.

1. A method for clarifying industrial laundry wastewater containingsurfactants, fats, oil and grease (FOG), total petroleum hydrocarbon(TPH) biochemical oxygen demand (BOD), chemical oxygen demand (COD),total suspended solids (TSS), ionized metals and other contaminantswhile minimizing sludge, comprising the steps of: (a) adding to thewastewater a water dispersed cationic blend whose major components areeffective amounts of both polydiallyldimethylammonium; chloride(pDADMAC) and aluminum chlorohydrate (ACH), the blend in a quantity ofbetween 50 ppm and 700 ppm, to break the emulsified bond in thewastewater and produce coagulated particles having sufficient mass andcationic charge to react with an anionic polymer flocculent to be addedthereafter; (b) delaying any flocculent addition by at least apredetermined time to permit the cationic blend to substantiallycomplete the coagulation of the particles in the wastewater in step (a);(c) adding to the wastewater aqueous anionic polymer flocculent in aneffective amount between about 5 ppm and 50 ppm and of sufficientmolecular weight and with a charge density of at least 35% so as toreact with the cationic charged coagulated particles to form flocculatedwaste particles of effective size to form sludge while leaving adisposable clarified water, thereby lowering the amount of sludgegenerated with respect to that normally generated using prior artcoagulation and flocculation techniques of adding additional coagulants,flocculents, coagulant aids, flocculent aids or sludge aids, includingbut not limited to, poly aluminum chloride, epi-amine coagulant,bentonite clay, perlite, ferrous sulfate, ferric chloride, anddiatomaceous earth; (d) separating the sludge from the clarified water;(e) passing the sludge to a plate and frame sludge press; (f) dewateringthe sludge by the press, thereby forming a disposable sludge cake; and(g) disposing of the sludge cake and the clarified water.
 2. The methodof claim 1 wherein the predetermined time in step (b) is on the order ofat least two seconds.
 3. The method of claim 1 wherein the anionicflocculent is essentially poly(acrylamide-co-acrylate).
 4. The method ofclaim 1 wherein the anionic flocculent is dry, further comprising thestep of: wetting the flocculent to a solution strength of about between0.05 and 0.50% prior to the adding step (c).
 5. The method of claim 1wherein the predetermined time in step (b) is on the order of at leasttwo seconds and the anionic flocculent is essentiallypoly(acrylamide-co-acrylate) added as a wetted solution having astrength of between 0.05 and 0.50% prior to adding in step (c).
 6. Themethod of claim 1 further comprising the step of: disposing of the waterfrom the dewatering step (f).
 7. The method of claim 1 wherein theanionic flocculent is dry, further comprising the step of: wetting theflocculent to a solution strength on the order of about 0.20% prior tothe adding step (c).
 8. The method of claim 1 wherein the predeterminedtime in which step (b) is on the order of at least two seconds, and theanionic flocculent is essentially a dry poly(acrylamide-co-acrylate),further comprising the steps of: wetting the flocculent to a solutionstrength of between about 0.05 and 0.5% prior to the adding step (c). 9.A method of clarifying industrial laundry wastewater containingsurfactants, fats, oil and grease (FOG), total petroleum hydrocarbon(TPH) biochemical oxygen demand (BOD), chemical oxygen demand (COD),total suspended solids (TSS), ionized metals and other contaminantscomprising the steps of: (a) adding to the wastewater a water dispersedcationic blend whose major components are effective amounts ofpolydiallyldimethylammonium; chloride (pDADMAC) and aluminumchlorohydrate (ACH), the blend in a quantity of between 50 ppm and 700ppm to break the emulsified bond in the wastewater and producecoagulated particles having sufficient mass and cationic charge to reactwith an anionic polymer flocculent to be added thereafter; (b) delayingany flocculent addition by at least a predetermined time to permit thecationic blend to substantially complete the coagulation of theparticles in the wastewater in step (a); (c) adding to the wastewater anaqueous anionic flocculent in an effective amount consisting essentiallyof poly(acrylamide-co-acrylate on the order of between about 5 ppm and50 ppm, and of sufficient molecular weight and charge density to reactwith the cationic charged coagulated particles to form flocculated wasteparticles of effective size to form sludge while leaving a disposableclarified water; (d) physically separating the sludge from the clarifiedwater without the use of secondary, tertiary or quaternary coagulationor flocculation aids; (e) passing the sludge to a plate and frame sludgepress; (f) dewatering the sludge by the press, thereby forming adisposable sludge cake; and (g) disposing of the sludge cake and theclarified water.
 10. The method of claim 9 wherein the predeterminedtime in step (b) is on the order of two seconds.
 11. The method of claim9 wherein the anionic flocculent is dry, further comprising the step of:wetting the flocculent to a solution strength on the order of between0.05 and 0.50% prior to the adding step (c).
 12. The method of claim 9wherein the predetermined time in step (b) is two seconds and theanionic flocculent is essentially poly(acrylamide-co-acrylate) added asa wetted solution having a strength on the order of between 0.05 and0.50% prior to adding in step (c).
 13. The method of claim 9 furthercomprising the step of: disposing of the water from the dewatering step(f).
 14. The method of claim 9 wherein the anionic flocculent is dry,further comprising the step of: wetting the flocculent to a solutionstrength on the order of 0.20% prior to the adding step (c).
 15. Themethod of claim 9 wherein the predetermined time in which step (b) istwo seconds, and the anionic flocculent is essentially a drypoly(acrylamide-co-acrylate), further comprising the steps of: wettingthe flocculent to a solution strength on the order of between 0.05 and0.50% prior to the adding step (c); and disposing of the water from thedewatering step (f).
 16. A method of clarifying industrial laundrywastewater containing surfactants, fats, oil and grease (FOG), totalpetroleum hydrocarbon (TPH) biochemical oxygen demand (BOD), chemicaloxygen demand (COD), total suspended solids (TSS), ionized metals andother contaminants, comprising the steps of: (a) adding to thewastewater an effective amount of a water dispersed cationic blendcomprising a combination of polydiallyldimethylammonium; chloride(pDADMAC) and aluminum chlorohydrate (ACH), the blend in a quantity ofbetween 50 ppm and 700 ppm to break the emulsified bond in thewastewater and produce coagulated particles having sufficient mass andcationic charge to react with an anionic flocculent to be addedthereafter; (c) delaying any flocculent addition by at least apredetermined time to permit the cationic coagulant blend tosubstantially complete the coagulation of the particles in thewastewater in step (a); (d) adding to the wastewater an aqueous anionicpoly flocculent, in an effective amount on the order of between 5 ppmand 50 ppm, of sufficient molecular weight and charge density of atleast 35% to react with the cationic charged coagulated particles toform flocculated waste particles of effective size to form sludge whileleaving a disposable clarified water; (e) separating the sludge from theclarified water; (f) passing the sludge to a plate and frame sludgepress; (g) dewatering the sludge by the press, thereby forming adisposable sludge cake; and (h) disposing of the sludge cake and theclarified water.
 17. The method of claim 16 wherein the predeterminedtime in step (b) is at least on the order of two seconds.
 18. The methodof claim 16 wherein the anionic flocculent is essentiallypoly(acrylamide-co-acrylate).
 19. The method of claim 16 wherein theanionic flocculent is dry, further comprising the step of: wetting theflocculent to a solution strength of between about 0.05 and 0.50% priorto the adding step (c).
 20. The method of claim 16 wherein thepredetermined time in step (b) is two seconds and the anionic flocculentis essentially poly(acrylamide-co-acrylate) added as a wetted solutionhaving a strength of between about 0.05 and 0.5% prior to adding in step(c).
 21. The method of claim 16 further comprising the step of:disposing of the water from the dewatering step (f).
 22. The method ofclaim 16 wherein the anionic flocculent is dry, further comprising thestep of: wetting the flocculent to a solution strength of about 0.20%prior to the adding step (c).
 23. The method of claim 16 wherein thepredetermined time in which step (b) is two seconds, the cationic blendis about 200% pDADMAC and 200% ACH and the anionic flocculent isessentially a dry poly(acrylamide-co-acrylate), further comprising thesteps of: wetting the flocculent to a solution strength of between about0.05 and 0.5% prior to the adding step (c); and disposing of the waterfrom the dewatering step (f).